<?xml version="1.0" encoding="utf-8"?>
<grammar xmlns="http://relaxng.org/ns/structure/1.0">
  <start>
    <ref name="element1"/>
  </start>
  <define name="element1">
    <element>
      <name ns="">foo</name>
      <oneOrMore>
        <choice>
          <empty/>
          <ref name="element2"/>
        </choice>
      </oneOrMore>
    </element>
  </define>
  <define name="element2">
    <element>
      <name ns="">bar</name>
      <empty/>
    </element>
  </define>
</grammar>
